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Identifying quantity

There are two basic complementary but different ways that we determine quantity:

  1. Counting
  2. Subitising.

The earliest form of recognizing quantity is described as subitising. Subitising is the direct and rapid perceptual apprehension of the numerosity of a group. The word subitise comes from the Latin “to arrive suddenly” (Kaufman, Lord, Reese, & Volkmann, 1949). Based on research into response times, subitising is generally associated with up to four objects in a random pattern.

With five or more items there is a dramatic increase in response times, suggesting counting may be occurring (Wolter, van Kempen, & Wijhuizen, 1987). The process of subitising is considered to be relatively effortless. The arrangement of the items also appears to have an impact on the response time with five or more items.

When students have developed knowledge of the number words associated with small quantities, subitising can be used to describe when a student is able to instantly recognise and allocate a number word to a small group of perceptual items. Kaufman used the term subitising to refer to verbal naming of the numerosity of the perceptual items. An example of subitising is naming the number of biscuits on a plate without having to count each biscuit. Fitzhugh (1978) found that some children could subitise sets of two, but were not able to count them. As none of these very young children were able to count any sets that they could not subitise, she concluded that subitising is a necessary precursor to counting.

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The regularity in a pattern can also contribute to an appreciation of how things fit together in space, known as spatial structure.